When a girls thighs are so skinny that they don't touch and form a rectangle with her vagina.

Source: The Sara and Aimee Podcast (SaraAndAimee.com)

A pick me is a woman that is willing to do anything for male approval. She will embarrass or throw other women under the bus to achieve this goal. The unfortunate thing about a pick me is usually the men they are trying to seek approval from are of poor quality and treat women badly, leaving little real benefit for the pick me.